This invention relates to a remote keyless entry system.
JP-A-8-284505 (hereinafter called the “reference 1”) describes a remote keyless entry system that executes 2-way communications, sends to an operation apparatus side a notice representing whether or not the operation is executed, and sends the report to a user. However, this reference does not describe a transfer data rate. Therefore, the reference does not take into account the decreasing of a communication distance in 2-way communications when it utilizes a weak radio wave. In other words, when communications fail at a place of a certain distance in the known reference 1, the operator must come into the range of the communication distance and must once again try communications.
JP-A-9-209630 (hereinafter called the “reference 2”) describes another remote keyless entry system. A portable transmitter of this system intermittently generates a radio wave modulated by an identification code, and when the user having the portable transmitter walks up to a car, a receiver mounted to the car receives the radio wave and releases the door lock when the identification code is correct. A time zone in which the portable transmitter automatically emits the radio wave for releasing the door lock can be set in order to minimize battery consumption.
Though the reference 2 limits the automatic transmission time zone, the transmitter executes an automatic output operation in a predetermined time zone either daily or on predetermined days of the week. Therefore, battery consumption is greater than when this automatic transmission operation is not made. Originally, a driver of a car desires to make the automatic door lock when the driver walks up to the car while holding things with his or her both hands and cannot take out a terminal board kept in the pocket, or when the driver approaches the car with an umbrella spread. Usually, when the driver returns to the car while holding things with both hands or with an umbrella spread, it does not take a long time before he reaches the car, and it is only five to 10 minutes, or about 60 minutes or so, at the longest. Therefore, it is not economical from the aspect of battery consumption to execute the automatic output operation in the predetermined time zone as is made in the reference 2.
JP-A-4-315684 (hereinafter called the “reference 3”) describes a remote keyless entry system in which a display is provided to a terminal board to display the state of a car. The driver of the car always keeps the key, and although the display is provided to the terminal board of the remote keyless entry system, the driver cannot confirm the time when he desires to check the time. Even when the time for operating the engine is determined in advance, the driver must take the trouble in walking up to the location of the car to start the engine.